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Child's IQ suffer if their mother is exposed to air pollution |
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Written by Phillip LaVeque
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Friday, 24 July 2009 |
Air pollution experienced by pregnant women may have a long-term impact on their children's intelligence, new research suggests. But it's not clear that any effect is big enough to be noticeable in a child's day-to-day life.
What do we know already?
Air pollution, from sources like traffic fumes and cigarette smoke, includes particles called polycyclic aromatic hydrocarbons (PAHs). Experiments on rats and mice have shown that these particles may affect the development of the brain.
Studies looking at children born in urban areas have suggested that higher levels of pollution may slow children's development. But it's hard to know whether pollution causes the problem, or whether there are other influences. Many children living in the most polluted areas are from poorer backgrounds, and may have poorer diet or education, for example.
A new study has looked at a group of pregnant women from similar backgrounds, living in the South Bronx and Washington Heights, New York. The women's exposure to PAH particles was measured during the last three months of their pregnancy, using pollution monitors. Their children were tested using a standard IQ test when they reached the age of 5.
What does the new study say?
Children whose mothers had breathed in the highest levels of PAHs during pregnancy scored 4 to 5 points lower on the IQ test. However, the average score of these children was still well within the average range of IQ for all children.
An average IQ is 100. Around half the population have a score between 90 and 109. In the study, the average score for children whose mothers were exposed to high levels of PAHs was 97. The average score for children whose mothers hadn't been exposed was 102.
After taking into account other factors, including the mother's own IQ, the difference between the groups was reduced, from about 5 points to 4.3 points. But it's hard to know exactly how much difference the lower IQ score would make to a child's life.
How reliable are the findings?
The study was carried out carefully, and the researchers tried to take into account other factors that could have skewed the results. The link seems likely to be real. But studies of this type can only show a link between pollution and IQ. They're not designed to prove that one thing causes another.
Where does the study come from?
The study was carried out in New York by researchers from Columbia University. It was published in Pediatrics, a medical journal owned by the American Academy of Pediatrics. It was funded with grants from the US National Institutes of Health and various charitable and educational foundations.
What does this mean for me?
The levels of pollution that these women experienced in New York were likely to be higher than those experienced by many women. And the study doesn't show for certain that traffic pollution caused the lower levels of IQ. Also, we don't know how much practical difference the 4 to 5 point drop in IQ might make. So, although it's never a good idea to breathe in more pollution than necessary, women shouldn't be too alarmed by this study.
What should I do now?
For an individual, avoiding pollution generally means taking fairly drastic steps, such as moving house. It's not realistic to make such big changes to your life based on a study like this. From a wider point of view, levels of PAH in the air could be reduced through tighter pollution controls, greater energy efficiency, and the use of alternative energy sources rather than fossil fuels.
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